The present invention generally relates to an improved system, method and apparatus for the manufacture of custom archery bowstrings.
The use of a flexed bow to propel an arrow towards a target dates to ancient times. The bowstring of a bow can be constructed of a wide variety of synthetic and natural fibers. Desired qualities for bowstrings are that the bowstring have high strength and limited elongation under tension, be durable, and respond predictably to the release of the drawn bow by the archer.
Archery bows are available in a wide variety of forms. Such forms include a longbow constructed of solid wood, such as yew, hickory or ash. An improvement of the longbow is the recurve bow, typically constructed of laminated wood, fiberglass or a combination of those or similar materials. FIG. 1 shows a diagram of a recurve archery bow, 40, strung with bowstring 42, with the bowstring ends 44 looped around the two bow arms or limbs 46, which are connected by grip handle 48. The longbow and recurve bow can be utilized with the bow and bowstring held in a vertical orientation, and the arm and fingers of the archer are used to draw the bow and release the drawn bowstring. The crossbow, an ancient variation of the longbow, in its modern form is often built with a recurved bow and attached bowstring held horizontally in a mount that allows the bow to be drawn and held in the drawn position. The crossbow can then be released at the archer's discretion using a mechanical release mechanism.
To preserve the elasticity of the bow, bows are usually stored with the string relaxed or unstrung. The simple bow, following ancient design, has a single bowstring that is either looped around the ends of limbs of the bow, looped around one end, and tied to the other limb, or tied to both limbs.
Archery technology departed from more than 2000 years of tradition with the invention by Allen of ‘An archery bow with drawforce multiplying attachment,” as described in U.S. Pat. No. 3,486,495, issued Dec. 30, 1969. The Allen bow is commonly called a “compound bow.” The compound bows sold today usually closely resemble the Allen bows, with a pair of eccentric cams mounted near the tips of the two limbs of the bow, with the bowstring wrapped around the each rotating cam and connected such that drawing the bowstring rotates the bowstring about the eccentric of each cam. The cams may also then be connected to a load cable that extends from the cam to an anchor on the tip of the opposite bow limb. This configuration provides for variable leverage exerted by the load cables while bending the bow limbs, such that the force required to hold the fully drawn bowstring is less than the maximum force required while the drawing of the bowstring. After 1969 the compound bow became increasingly popular, such that by the year 1980 the majority of bows and crossbows sold were compound bows. FIG. 2 shows a diagram of a typical compound archery bow, 50, strung with compound bowstring 52. Compound bowstring 52, beginning with ends 54, passes over pulleys 55 and 56 before reaching an attachment at the end of one of limbs 57, which are supported by grip handle 58.
Two forms of bowstrings are commonly used with simple bow, the continuous bowstring, and the Flemish bowstring. The Flemish bowstring has a loop at one end, and a free end (for tying) at the other. In certain applications, a number of individual strings are attached end to end to provide sufficient length, and to allow replacement of worn portions.
The so-called continuous bowstring is formed of an elongated length of bowstring body fiber that is used to form a loop of bowstring fiber, then end loops are formed by wrapping a portion of the bowstring body fiber with serving fiber in order to form a loop and add protection to the end loops which are areas of high wear. The typical compound bow has two to three bowstrings. If these bowstrings were a single bowstring, the single bowstring would typically be three times as long as the string for a recurve bow of similar size.
The manufacture of bowstrings is in part difficult because the length of bowstring needed varies substantially between different models of bows, and the type of bowstring may vary for different applications, relating to drawforce, and the sport in which the bow is used. Thus, archery practitioners rely on the manufacture of a wide variety of slightly different bowstrings, often times relying on their own skills to manufacture a needed bowstring, or being forced to wait through long delivery periods while a custom bowstring is delivered. Archery shops are unable to stock the enormous number of different bowstrings that would be needed to service all bows available to archers, thus rarely hold in stock more than the most common bowstrings. As a service to their customers, certain archery shops have become skilled at the custom construction of bowstrings. To this day, almost all construction of bowstrings at local shops is by hand winding of serving cord around bowstring fibers, often on a one of a kind jig. There exists the continuing need for a machine that could speed the rate at which bowstrings can be manufactured and that allows for the custom manufacture of bowstrings that meet individualized needs in terms of size, twist rate, materials and weight.
A number of previous types of apparatus contain elements that may be useful in the manufacture of bowstrings. For instance, U.S. Pat. No 3,616,061 to J. W. Carter, issued Oct. 26, 1971 discloses a powered apparatus that traverses along two axes and winds one elongated material over a second elongated material that is stationery during winding. This apparatus provides spools that rotate around a core, with longitudinal displacement controlled by pulley system. U.S. Pat. No 3,882,662 discloses a bowstring server that wraps along a bowstring. U.S. Pat. No. 4,013,500 discloses an apparatus for wrapping flower stems. U.S. Pat. No 4,663,928 to Delobel, et al, issued May 12, 1987 discloses a machine for winding single strands of protective wire over a multiple stranded core. The machine is adapted for wrapping a cable that moves though the winding head, and is not adaptable for wrapping a fixed cable at several optional locations along its length. U.S. Pat. No. 4,824,036 discloses an apparatus for spiral winding of strands of hair.
A number of types of apparatus that would be adaptable to wrapping serving cord around a bowstring are typified by U.S. Pat. No. 6,401,442 to Root, et al., issued Jun. 11, 2002, disclosing an apparatus for dubbing or wrapping fly body material around a hook during assembly in fly hook production. The fibers forming the body of the wrapped body are rotated around one fixed end. Other apparatus could rotate the entire boy fibers relative to serving cord. Systems such as this suffer from limitations in maintaining finished length, as is needed in bowstrings, and variation in the relative twist of the fibers.
U.S. Pat. No. 5,538,197 to Killian, issued Jul. 23, 1996 shows one portable power driven serving apparatus known in the art. The apparatus provides a gear driven serving tool that is latched around a bowstring, activated to wrap serving, essentially as a hand serving tool would do, and the unlatched and moved to another position. A similar device is disclosed in U.S. Patent Publication No 2004/0046079 by Coy, that discloses a bowstring serving tool with a dedicated power source that is hand held. In the Coy device, a slotted disk carrying a serving tool is rotated about a center point by motor driven bevel gears. No provision is made to assure proper indexing of serving cord and regularity of applied serving.
Thus no available apparatus provides an integrated machine capable of uniformly, and efficiently applying serving around a fiber bundle. There exists a continuing need for such an apparatus that allows for the rapid construction of bowstrings of a desired length and with performance characteristics of predictable quality.